Thermostatic switch



u y 1941- w. H. FISCHER 2,248,666

THERMOSTATIG SWITCH Filed Nov. 25, 1958 IN VENTOR.

' h/////d/77 fircfier Patented July 8, 1-941 THERMOSTATIC SWITCH William H. Fischer, Des Plaines,- Ill., assignor to Dominion Electrical Manufacturing, Inc.

Application November 25, 1938, Serial No. 242,159

7 Claims.

My invention relates to thermostats and switches and more particularly to a thermostat and a switch which can be operated from the same control knob.

An object of my invention is to provide a thermostat control and a switch control on one control knob.

Another object of my invention is to simplify the controls of an electrically heated appliance by combining the thermostat control and the switch control.

Another object of my invention is to cut the costs of manufacturing an electrical appliance by combining several controls.

Still another object of my invention is to provide more accurate means for adjusting the thermostat than, has hitherto been used in connection with the switch control. I

A further object of my invention is to provide a simple and convenient adjustment in connection with the switch control and the thermostat control for adjusting the thermostat to compensate for loss of resiliency in the resilient members and for permanent change in the length of the thermostatic member.

A still further object of my invention is to combine three regulatory means on one control shaft,

each to operate separately on one thermostat to simply and accurately control the thermostat, thereby producing an inexpensive but well regulated electrical appliance.

Another object of my invention is to provide a thermostatic switch which may be manually operable to turn electricity on and off at will and which may be adjustably set to automatically turn the electricity on and off depending upon the temperature setting and the temperature of the electrically heated appliance. Other objects and a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure l is a side elevation view of a thermostat constructed in accordance with my invention and showing a control knob mounted on a part of an electrical appliance;

Figure 2 is a cross-sectional view of my thermostat taken along the longitudinal centerthere- Figure 3 is another cross-sectional view of my knob of my invention; I

Figure 5 is a side elevational View of a shoe position of my invention, and

Figure 6 is a top view of the shoe shown in Figure 5.

With reference to Figure 2 of the drawing, it will be noted that my invention comprises a thermostatic switch assembly Ill comprising a substantially U-shaped channel temperature responsive member H which is designed to rest flat on a heated surface such as the sole plate 9 of an electric iron, or other electrical appliance.

On top of the U-shaped channel temperature responsive member ll there is a flat top piece l2 which is secured to the U-shaped channel member by means of projections l3 on the U- shaped channel member being inserted through slots in the flat top piece and upset to form virtually a rivet head. Inside the case which is formed by covering the open part of the U- shaped channel temperature responsive device II with the flat top piece I2 and at the bottom of thechannel there is fastened, by rivets IT, to the temperature-responsive piece H a flat steel spring l4. As can be best seen in Figure 2 the steel spring [4 is crimped upwardly to form a raised portion l5 which supports an insulated engaging member l6.

Above the insulated engaging member l6 and urged upwardly by it is a resilient contact strip 20 which carries current into the thermostat from an outside source l8. Above the resilient contact strip 20 and spaced from it when uncon strained is a second resilient contact strip 2| which passes the current to the heating element by means of conductors l9. Between the two contact strips and arranged to engage each other if either strip is actuated, are a pair of contact points 21 and 28 respectively secured to the strips 20 and 2|. Suspended above the strip 2| is an L-shaped suspended member 23 pivotally secured to the top of the U-shaped channel, member H. To the suspended member 23 there is attached an insulated engaging member 26 which is adapted to engage the strip 2| and press it down when the suspended member 23 is turned. The suspension member 23 is actuated by an actuating device which comprises a handle or knob 36 mounted on a revolvable shaft 31 through the casing 38 of an electrical appliance. I

A swinging arm 39 is suitably attached to-the revolvable shaft,3'l. by upsetting the end of the shaft to form a rivet head. The swinging arm 39 is adapted to fit between the bifurcated arm of a second swinging arm 40 which is attached to a rotatable hollow threaded shaft 45.

0n the fiat top piece l2 there is mounted a collar 4'! having female threads .for threadably re ceiving the hollow threaded shaft 45 which may be adjustably moved up and down as the knob 85 is turned. Adjustably secured to the lower end of the hollow rotatable shaft 45 by means of extending ears 55 slidably fitting in longitudinal slots 53 and rotatable with the shaft is an engaging shoe 54 having an engaging surface 48 at its base. The engaging surface 48 is substantially flat with the exception of a relieved portion 49. The fiat portion may be described as the on portion and relieved portion as the oiT' portion. Below the engaging surface 48 there extends a small projection 51 which fits into a hole in the L-shaped suspension member 88. Extending above the L-shaped suspension member and positioned to be under the rotating shoe 54 is a raised portion 58, which may be made by slitting the suspension member 28 and bending the raised portion 58 upward as can be seen in Figure 5. Bending the raised portion 58 foreshor-tens it and provides a slot into which the engaging member 25 may be positioned.

When the knob 35 is turned to its oil position the shoe 54 is rotated until the relieved portion 49 is above the raised portion 58. The resilient contact strip 2| then forces the suspension member 28 upward until the raised portion causes the threaded actuating shaft to screw farther into the collar 41 thereby constraining the suspension member 28 to push the contact strips 28 and 2| farther down. This action causes the lower contact strip 28 to be bent about the insulated engaging member |5 as a fulcrum.

58 touches the relieved portion 48. This upward movement allows the contact points 21 and 28 to separate thereby preventing the flow of current through the contact strips 28 and 2|. When it is desired to turn the electrical apparatus on the knob 85 is rotated to the on position thereby causing the threaded "shaft 45 to rotate within the stationary collar 41 and positioning the flat on" portion of the engaging surface 48 above the raised portion 58. Thus, by the double action of the downward movement of the threaded shaft 45 and the downward displacement of the suspension member 28' by the fiat portion of the engaging surface 48 the suspension member 28 is constrained against the resilient contact strip 2| forcing it downward into contact with the contact strip 28 thereby allowing electric current to flow through the apparatus.

The U-shaped channel member together with the crimped spring N form the temperature responsive element of the thermostatic switch. ,As the electrical apparatus heats up the U- shaped channel member expands longitudinallyat a rate greater than the expansion of the crimped steel spring l4. This is'because the U-shaped channel member II is preferably made of aluminum while the" crimped spring I4 is made of steel which has a much lower coefficient of expansion than the aluminum. This difference in expansion allows the U-shaped aluminum channel member .H to stretch the crimped steel spring |4 thereby causing the-insulated engaging member ii to drop down and allow the resilient contact strip 28, which has been constrained upward, to move away from the contact strip 2| thereby breaking the electrical circuit. When the apparatus has cooled' due to the breaking of the electrical circuit the- U-sh'aped channel member shrinks forcing the ends of the crimped steel spring l4 together and the attached insulated engaging member" upward thereby constraining the contact strip 28 in contact with the contact strip 2| to re-establish the electric circuit and re-heat the apparatus.

When it is desired to regulate the temperature to which the apparatus may be heated after the contact between points 21 and 28 is made, the actuating device 85 isturned farther an The farther down the-contact strip 28 is bent, the farther out the U-shaped channel member must stretch to allow the crimped steel spring H to drop sufiiciently to break the contact between the points 21 and 28.

The steel spring |4 serves another purpose beside constraining the contact strip'28. It imparts a longitudinal compressive force to the U-shaped channel member H which is necessary to counteract the growing tendency which all aluminum parts which are alternately heated and cooled have. The combination of the aluminum U- shaped channel member H and the steel spring |4,is shown, described and claimed in application Serial No. 187,883, filed January 31, 1938,

by William A. Barnes for Temperature responsive device and assigned to the Dominion Electrical Manufacturing Company now Patent No. 2,217,328 dated October 8, 1940.

An adjustment 52 is used to accurately set the temperature of the electrical appliance and make the settings coincide with the markings on the control knob 88 before the instrument leaves the factory. The adjustment 52 comprises a threadable set screw 58 in the hollow rotatable shaft 45. When it is desired to adjust the temperature, the set screw 88 is turned with respect to the hollow rotatable shaft 45 thereby shifting the engaging shoe 54 with "respect to the stationary collar 41.

To support the contact strips 28 and 2| I have provided a clamp 55 made of insulating material. This clamp comprises a top insulator 81, a bottom insulator 58 and a mica sheet 88, with bolts 1| therethrough and the whole attached to the flat toppiece |2 by nuts 12. The contact strip 2| is placed next to the lead I8 which is connected to the heating element between the .top and bottom insulator blocks and the contact strip 28 is placed next to the outside current source |8 between the mica sheet 58 and the bottom insulator block 88.

The bolts 1| pass through the various contacts but spaced therefrom and through the clamp 55 and are fastened to the flat top piece H by means of the nuts 12.

Figure 4 is a top view of the control knob 88 having a graduated scale 84 and an indexing arrow 85 placed on the appliance. The knob '85 is rotatable with respect to the stationary indexing arrow 85 and the registration of the scale 84 with the arrow 85 indicates the operating condition of the appliance.

Summarizing, it 'is noted that my invention comprises the two contact strips 28 and 2|, the manually operable actuating device .85 for constraining the strips 28 and 2| together or for allowing them toseparate and the temperature responsive means for constraining the strips 28 and 2| together or for allowing them. to separate.

,The two contact strips 28 and 2| are mounted in the insulated clamp 85 in such a manner that they are normally resiliently disposed to separate from each other. The manually operable actuating device 85 is comprised of the threaded stem 45, the stationary collar 41, and the engaging shoe 54. The shoe- 54 which has a flat on" portion 48 and an inclined "off portion 49 is rotatively connected to the threaded stem 45 by means of the projecting ears 55 which fit into the slots 53 in the stem. The slots 53 allow the engaging shoe 54 to move axially with respect,-

to the threaded stem 45 when the adjusting screw 63 is turned to set the temperature of the appa- 45 is turned to influence the contact strips 20 and 2| independent of the inclined portion 49 of the engaging shoe 54. After the thermostat has been set and the switch turned on the temperature of the apparatus is governed by the U-shaped channel member II and the crimped spring 14 expanding and contracting to allow the contact strip 20 to drop away from or touch the ,contact strip 2i.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to' without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. In an electrical appliance, a thermostatic switch comprising, in combination, first and second relatively movable contacts normally resiliently disposed to separate from each other, hollow threaded means, inclined means rotatively -connected to said hollow threaded means, axial means in said hollow threaded means for adjustably setting the inclined means with respect to said hollow threaded means to influence the temperature setting of the said thermostatic switch, said hollow threaded means and said inclined means being manually rotatable together to move the first of said contacts to make a circuit with the second contact or to allow said first contact to spring away from said second contact to break the circuit, a temperature responsive element operable upon said second contact to make or break the circuit depending upon the temperature of the said electrical appliance, said hollow threaded means being operable separately from said inclined means to move both of said contacts to regulate the temperature setting of the said thermostatic switch.

2. In an electrical appliance, a thermostatic switch comprising, in combination, first and second relatively movable contacts normally resiliently disposed to separate, hollow threaded regulating means, adjustable shoe means having a flat on portion and an inclined off portion,

said adjustable shoe means being 'rotatively engagement with said second contact, said displacement being the sum of the thread displacement and the displacement of the on portion of the shoe means, and a temperature responsive element operable upon said second contact to make or break the circuit depending upon the temperature of the said electrical appliance, said hollow threaded regulating means being operable separately from said inclined ofi portion of the adjustable shoe means to move both of said contacts to regulate the temperature setting of the said thermostatic switch.

3. In an electrical appliance, a thermostatic switch comprising, in combination, a pair of relatively movable conductors normally resiliently disposed to separate, hollow regulating thread means, shoe means having a regulating on portion and a relieved off portion and adapted to turn as said hollow regulating thread means turns, actuating means for turning said hollow regulating thread means, motion transmitting means positioned between said conductors and said shoe means and resiliently kept in contact with the shoe means by one of the resilient conductors, said off portion of the shoe means permitting the motion transmitting means and one of said conductors to move away from the other conductor, and said regulating on portion of the shoe means in combination with the regulating thread means causing said motion transmitting means to move the conductors to regulate the temperature setting of the said thermostatic switch, and means in said hollow regulating means for regulating the temperature setting of the thermostatic switch independently of said actuating means.

4. In an electrical appliance, a thermostat switch comprising, in combination, first and second relatively movable contacts normally resilientl disposed to separate, hollow threaded regulating means, adjustable shoe means having a fiat on portion and an inclined off portion,

said adjustable shoe means being rotatively con-' nected'to said regulating means, axial means in said hollow threaded regulating means for adjustably setting the inclined means with respect to said regulating means to influence the temperature setting of the said thermostatic switch, said regulating means and said adjustable shoe means being rotatable together to displace the first of said contacts into engagement with said second contact, said displacement being the sum of the thread displacement and the displacement of the on portion of the shoe means, and a temperature responsive element operable upon said second contact to make or break the circuit depending upon the temperature of the said electrical appliance, said threaded regulating means being operable separately from said being rotatable together to effect a quick make or break between said contacts by the total displacement of the threads on the shaft and the rapid transition on the shoe means, said shoe means and said threaded shaft also being rotatable together to form a regulating means able with respect to said threaded shaft to alter the position of the shoe means with respect to bination, a pair of relatively movable contact arms fixed at one end and free at the other end, a movable contact on the free end of each of said pair of contact arms, temperature responsive means for moving the first of said contacts, said temperature responsive means engaging the first of said contact arms at a fulcrum point between said fixed end and said contact, and manually operated means for moving the second of said contacts to provide an on and off switch for said thermostatic switch and for bending the first of said contacts about the said fulcrum point to regulate the temperature of the said thermostatic switch, said manually operated means comprising a turnable shaft for actuating the second of said contacts and a calibrating means for changing the length of said turnable shaft to adjust the temperature setting of the said thermostatic switch.

'7. In an electrical appliance, a thermostatic switch, comprising, in combination, a pair of resilient arms each being mounted at one end and free at the other end, contacts mounted on the free ends of said resilient arms for regulating the electrical circuit through'the said appliance manually operable means for engaging one of said resilient arms between the said contact and the said fixed end to manually regulate the thermostatic switch, thermostatic means for engaging the other of said resilient arms between the said contact and the saidfixed end to automatically regulate thethermostatic switch, said manually operable means comprising a hollow regulating means and a calibrating means mounted therein, said calibrating means being adapted to adjust the engagement relationship between the said manually operable means and the said resilient arm engaged thereby to affect the regulating action of the manually operable means upon the thermostatic switch.

WILLIAM H. FISCHER. 

